NE 555 (On , Off, ON) when subjected to different input voltage

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MrsssSu

Joined Sep 28, 2021
181
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Hi readers, :)
I found this at Click here
This is an example of a disconnect and reconnect circuit using NE555. This means that the state of load will be (High, then, Low, them High). However, when I simulated using LT Spice it just give me (Low and High only). Does anyone know how to make the state of the load (High, then, Low, them High) when subjected to voltage change. For example, V2 below 12V, load is ON, then when V2 reach 12V, it will be OFF, then when V2 reach 15V, it will be ON again.

Is it possible to do this with NE 555 IC ? My LT Spice file below for reference
 

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crutschow

Joined Mar 14, 2008
29,508
I don't offhand see how to do that with a 555, but it can be done with two comparators (e.g. LM339/393) configured as a window comparator (example below).
You can wire AND the outputs of the LM339 since they are open collector.

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crutschow

Joined Mar 14, 2008
29,508
If you want to use this to control battery charging, you can use a voltage reference, such as the TL431, along with a voltage divider to provide stable trigger points.
 

Alec_t

Joined Sep 17, 2013
12,744
Is it possible to do this with NE 555 IC ?
Yes. Like this :
OffOnOffControl.jpg
Potential-divider R3/4 sets the 'less than 12V' point. Potential-divider R1/2 sets the 'above 15V' point. You may need to tinker with the resistor values to get the exact voltage trip points that you want. The '555 output goes to your relay coil.
 

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Last edited:

Alec_t

Joined Sep 17, 2013
12,744
Indeed, temperature will affect the trip point, but this may not be critical for the intended use. Simulation shows the 12V trip point varies by about 300mV over a temperature range of -10°C to +40°C, whereas the 15V trip point shows no variation. Vcc should be pretty stable as it's provided by a 7805.
 
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